Biocontrol of a root-rot disease complex of chickpea by Glomus intraradices, Rhizobium sp and Pseudomonas straita

The effects of Glomus intraradices, Rhizobium sp. and Pseudomonas straita on the root-rot disease complex of chickpea caused by Meloidogyne incognita and Macrophomina phaseolina were observed. Inoculation of G. intraradices, P. straita and Rhizobium caused a significant increase in plant growth, number of pods, chlorophyll, nitrogen, phosphorus and potassium contents of pathogen-inoculated plants. Inoculation of Rhizobium caused a greater increase in plant growth, number of pods, chlorophyll, nitrogen, phosphorus and potassium contents of pathogen-inoculated plants than caused by P. straita or G. intraradices. Combined inoculation of G. intraradices with P. straita plus Rhizobium to pathogen-inoculated plants caused greater increase in plant growth, number of pods, chlorophyll, nitrogen, phosphorus and potassium contents than by inoculation of G. intraradices plus Rhizobium or G. intraradices plus P. straita. The numbers of nodules per root system were significantly higher in plants inoculated with Rhizobium compared with uninoculated ones. Inoculation of Rhizobium with P. straita/G. intraradices further increases nodulation per root system over plants inoculated with Rhizobium alone. Root colonization by G. intraradices was high in plants inoculated alone. In the presence of P. straita and Rhizobium, root colonization by G. intraradices was increased, while inoculation of pathogens reduced colonization by G. intraradices. Inoculation of Rhizobium caused higher reduction in galling and nematode multiplication, followed by P. straita and G. intraradices. Maximum reduction in galling and nematode multiplication was observed when G. intraradices was inoculated with both bacteria. Biocontrol of root-rot disease complex of chickpea may be achieved by the combined use of Rhizobium, G. intraradices and P. straita or use of Rhizobium plus P. straita. (C) 2007 Elsevier Ltd. All rights reserved.